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Versions: 00 01

Transparent Interconnection of Lots of                             Q. Wu
Links Working Group                                               W. Hao
Internet-Draft                                                    Huawei
Updates: 6325 (if approved)                             October 22, 2012
Intended status: Standards Track
Expires: April 25, 2013


     LSP extension for Tree Distribution Optimization across sites
                draft-wu-trill-lsp-ext-tree-distr-opt-01

Abstract

   This document specifies an extension to LSP for the Rbridge in one
   site to advertise Global VLAN scope and associated link attribute to
   all the Rbridges both in the site of that Border Rbridge and the
   other adjacent sites in the same campus.  With this extension,
   RBridges can prune the distribution tree of multi-destination frames
   according to the scope of the VLAN and link attribute defined in this
   document.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 25, 2013.

Copyright Notice

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   document authors.  All rights reserved.

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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions used in this document  . . . . . . . . . . . . . .  4
   3.  Motivations  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  TLV and Sub-TLV Extensions to IS-IS for Inter-site
       Distribution Tree  . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Global-VLANs Sub-TLV for the Router Capability TLV . . . .  6
       4.1.1.  Definition of Fields in Sub-TLV  . . . . . . . . . . .  6
     4.2.  Link-Attributes Sub-TLV extension for extended IS
           reachability TLV . . . . . . . . . . . . . . . . . . . . .  7
   5.  Use of TLV and Sub-TLV for Tree Distribution Optimization
       across sites . . . . . . . . . . . . . . . . . . . . . . . . .  8
   6.  Unicast Forwarding Consideration . . . . . . . . . . . . . . . 11
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Appendix A.  Change Logs . . . . . . . . . . . . . . . . . . . . . 16
     A.1.  draft-wu-trill-lsp-ext-tree-distr-opt-01 . . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17























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1.  Introduction

   Large datacenters are often multi-site in nature and may contain a
   large number of Rbridges in each site.  A trill Campus network may
   also be designed to be multilevel can be divided in to multiple IS-IS
   [IS-IS][RFC1195]L1 Areas interconnected by L2 backbone area.  Routing
   between Rbridges within a IS-IS L1 area/ site is known as "Level 1
   routing".  Routing between IS-IS L1 areas or sites is known as "Level
   2 routing".  The IS-IS L1 area supports Level 1 routing and consists
   of Rbridges within the site and link between Rbridges within the
   site.  The L2 backbone area supports Level 2 routing and consists of
   Border Rbridges and links between the Border Rbridges.  Border
   Rbridges may participate in one or more L1 areas as Level-1 Rbridges
   inside each site, in addition to their role as Level 2 Rbridge across
   sites.

   In Trill campus network, RBridges use distribution trees to forward
   multi-destination frames.  In case of one Trill campus network having
   multiple sites, the traffic associated with some distributed trees
   may travel between sites while the traffic associated with other
   distributed trees may be limited to only one site and not allowed to
   go across other sites.  The traffic spanning across sites is also
   referred to as the traffic with global scope.  In order to support
   scaling and performance of large TRILL networks in the real
   deployments, it is desirable to forward most of Multi-destination
   Trill traffic within the site and reduce the traffic that is required
   to span across sites within the entire TRILL campus.  According to
   The TRILL base protocol, each distribution tree SHOULD be pruned per
   VLAN.  When it is inevitable to construct trees that have a scope
   across sites throughout the TRILL campus, it is necessary to treat
   traffic tagged with VLAN differently based on VLAN scope and distinct
   the link between Rbridges in one site and link between two Border
   Rbridge in two sites to support large scale multi-tenants
   application.

   This document specifies an extension to LSP for the Rbridge in one
   site to advertise Global VLAN scope and associated link attribute to
   all the Rbridges both in the site of that Border Rbridge and the
   other adjacent sites in the same campus.  With this extension,
   RBridges can prune the distribution tree of multi-destination frames
   according to the scope of the VLAN and link attribute defined in this
   document.









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2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC2119 [RFC2119].














































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3.  Motivations

   Distinguishing global vlan from local vlan is to increase the number
   of tenants by not breaking the VLAN tag size limits.  E.g. one campus
   being divided into n sites, without distinction between global vlan
   and local vlan, at most support 4K tenants.  However, if we
   distinguish global vlan from local vlan, suppose each site support
   only local vlan.  Then each site support 4K tenants, the total number
   of tenants supported by one campus can be increased to 4n*K.Suppose
   some sites support local vlan, some sites support both local vlan and
   global vlan, the total number of tenants supported by one campus
   (4K,4n*K).







































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4.  TLV and Sub-TLV Extensions to IS-IS for Inter-site Distribution Tree

   This section describes data formats and code points for the TLVs and
   sub-TLVs added to IS-IS defined by this specification to support the
   multi-level TRILL or re-used from that already contained in the
   standard IS-IS extensions defined in [RFC6326].

4.1.  Global-VLANs Sub-TLV for the Router Capability TLV

   The optional Global-VLANs sub-TLV specifies the VLANs that have
   global scope and enable Construction of global multi-destination
   trees among different sites.  It has the following format:

      +-+-+-+-+-+-+-+-+
      |     Type      |                  (1 byte)
      +-+-+-+-+-+-+-+-+
      |   Length      |                  (1 byte)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | RESV  |  Start VLAN ID        |  (2 bytes)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | VLAN bit-map....
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: Report Block Structure

4.1.1.  Definition of Fields in Sub-TLV

   Type: 8bits

      Router Capability sub-TLV type, set to TBD (GLOBAL-VLANs).


   Length: 8bits

      Variable, minimum 3.


   RESV: 4bits

      4 reserved bits that MUST be sent as zero and ignored on receipt.


   Start VLAN ID:12bits

      The 12-bit VLAN ID that is represented by the high order bit of
      the first byte of the VLAN bit-map.





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   VLAN bit-map:

      The highest order bit indicates the VLAN equal to the start VLAN
      ID, the next highest bit indicates the VLAN equal to start VLAN ID
      + 1, continuing to the end of the VLAN bit-map field.


4.2.  Link-Attributes Sub-TLV extension for extended IS reachability TLV

   The link-attribute sub-TLV is carried within the TLV 22 and has a
   format identical to the sub-TLV format used by the Traffic
   Engineering Extensions for IS-IS ([RFC3784]): 1 octet of sub-type, 1
   octet of length of the value field of the sub-TLV followed by the
   value field -- in this case, a 16 bit flags field.

   The Link-attribute sub-type is 19 and the link-attribute has a length
   of 2 octets.

   This sub-TLV is OPTIONAL and MUST appear at most once for a single IS
   neighbor.  If a received Link State Packet (LSP) contains more than
   one Link-Attribute Sub-TLV, an implementation SHOULD decide to
   consider only the first encountered instance.  The following bit is
   defined:

   Public Link Type For TRILL(0x03)  When set, this indicates that the
      link is public link for TRILL sites interconnection.

























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5.  Use of TLV and Sub-TLV for Tree Distribution Optimization across
    sites

   When the TRILL campus is divided into multiple sites, each site may
   have one or more Border Rbridges used to interconnect other remaining
   sites and form the Level 2 IS-IS Trill network.  Such Level2 IS-IS
   Trill network can be used to construct global multi-destination tree
   spanning across various sites.

        TRILL Site 1                              TRILL Site 2
   +-------------------+  +---------------+   +-------------------+
   |                   |  |               |   |                   |
   | +---+      +----+ |  |      WAN      |   |+----+       +---+ |
   | |RB1|------+BRB2| |--|L2 Connectivity|---||BRB3|-------|RB4| |
   | +---+      +----+ |  |               |   |+----+       +---+ |
   |                   |  |               |   |                   |
   +-------------------+  +---------------+   +-------------------+
                                   |
                                   |
                         +-------------------+
                         |      +----+       |
                         |      |BRB5|       |
                         |      +----+       |
                         | +---+   |   +---+ |
                         | |RB6|---+---|RB7| |
                         | +---+       +---+ |
                         +-------------------+
                             TRILL Site 3

        Figure 1: Example of multiple sites within one Trill Campus

   In order to support scaling and performance of large TRILL networks
   in the real deployments, firstly, not all the links between the level
   2 Rbridges need to be used to Construct global multi- destination
   trees.  If the link between the level 2 Rbridges is allowed to
   construct global multi-destination trees, we can set this link
   attribute into "public interface for global tree construction".  In
   this document, we reuse Link Attribute sub-TLV for the extended IS
   reachability TLV and allocate a new bit value inside link Attribute
   Sub-TLV to support indication of "public link for global tree
   Construction".  The Border Rbridge in one site need to advertise this
   link attribute Sub-TLV to all the neighboring Border Rbridges in
   other neighboring sites and then this sub-TLV will be further
   forwarded to all the Rbridges in the site of each neighboring Border
   Rbridge.  RBridges in each site can prune the distribution tree of
   multi-destination frames according to such link attribute.

   Secondly, not all traffic should have global scope and need to span



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   across sites.  Since each distribution tree SHOULD be pruned per VLAN
   according to [RFC6325], we can specify a set of Global VLANs to
   identify the traffic that has global scope.  In this document, we
   define one new sub-TLV for the Router Capability TLV, i.e., Global-
   VLANs Sub- TLV.  This Sub-TLV can be used by Rbriges in one site to
   determine whether Construction of global multi-destination trees
   across sites is allowed.  In order to achieve this, the tree root or
   highest priority RBridge in one site configured to know a number of
   appropriate VLANs as Global VLANs and announce such information to
   the nearest border Rbridge; Then such Border Rbridge in this site
   need to advertise Global VLAN Sub-TLV to all the neighboring Border
   Rbridges in other neighboring sites and then this sub-TLV will be
   further forwarded to all the Rbridges in the site of each neighboring
   Border Rbridge.  When Global VLAN and link attribute Sub-TLV
   described above has been distributed to all the corresponding
   Rbridges in the downstream of the tree root or highest priority
   RBridge, RBridges can prune the distribution tree of multi-
   destination frames according to the scope of the VLAN and link
   attribute defined in this document, eliminating branches that own
   link type mismatching with Distribution Tree scope identified by
   VLAN.  If the distribution tree is local tree and has branches
   including a link with link attribute is set to public link for global
   tree construction, those branches should be eliminated.  If the
   distribution tree is global tree and has branches containing a link
   with link attribute not set to public link for global tree
   construction, those branches also should be eliminated.

























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             +---+
             | a |
             +---+
        L1 \       \  L2
         \           \
        \              \
      +---+           +---+
      | b |           | c |
      +---+           +---+
                 L3  \      \ L4
     VLAN20         \         \
                  \             \
                +---+         +---+
                | d |         | e |
                +---+         +---+
                  _             _
                  _             _     \
   public link    _L5           _L6     \ L7
                  _             _         \
                +---+         +---+      +---+
                | f |         | g |      | h |
                +---+         +---+      +---+

                VLAN10        VLAN10    VLAN20

                        Figure 2: Distribution Tree

   Take distribution tree in Figure 2 as an example, Rbridge a is root
   node.  Rbridge f,g are leaf nodes that have end station on VLAN 10
   while Rbridge b,h are another two leaf nodes and that have end
   station on VLAN 20.  The link between Rbridge d and f is public link
   used across sites while the other links in the figure 2 are links
   owned by one single site.  Assume VLAN 10 are local VLAN and VLAN 20
   are Global VLAN, after distribution tree pruning is done, Rbrige c
   should eliminate branch that has Rridge d and f since distribution
   tree is pruned based on local VLAN 10 and Link 5 in that branch is
   public link, which mismatch with each other.














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6.  Unicast Forwarding Consideration

   In unicast forwarding, the MAC forwarding table for a Trill Border
   Rbridge is usually learned through the data plane, i.e.,MAC address
   is learnt from received Broadcast,Unknown, Unicast,Multicast packet
   through distribution tree.  For end stations on the local vlan, the
   broadcast scope is limited to one local site, the Border Rbridge only
   learns MAC address of locally attached end station and the forwarding
   path between end stations within one site can be built for unicast.
   For end stations on global VLAN, end stations between two sites are
   within the same layer 2 broadcast domain, the Border Rbridge can
   learn MAC address of end stations across sites and the forward path
   between two sites can be built as well for unicast.  Therefore
   unicast forwarding between sites can be controlled through LSP
   extension we defined in this document.

   If the Border Rbridge is statically configured with unicast
   forwarding table and the nickname of the destination Rbridge is
   specified as one Rbridge's nickname in other sites, the unicast
   packet must be forced to forward to the other sites.  In this case,
   the Border Rbridge in other sites performs security check to the
   received packet.  If the VLAN associated with the received packet is
   local VLAN and the packet is ingressed from public link across site,
   the packet should be discarded.  If the VLAN associated with the
   received packet is Global VLAN, the packet should be allowed to
   ingress from public link across sites.

























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7.  IANA Considerations

   IANA is requested to assign a new codepoint for the Global-VLANs Sub-
   TLV defined in this document and carried within TLV 242.

   IANA has created a registry for bit values inside the link-attributes
   sub-TLV called "link-attribute bit values for sub-TLV 19 of TLV 22".

   This document instructs IANA to add a new bit value in the link-
   attribute bit values for sub-TLV 19 of TLV 22 registry as follows:

   Value   Name                              Reference
   -----   ----                              ---------
   0x3    Public Link Type between sites   [This document]

   Further values are to be allocated by the Standards Action process
   defined in [RFC2434], with Early Allocation (defined in [RFC4020])
   permitted.

































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8.  Security Considerations

   The security considerations documented in [RFC4971][RFC5305] are
   applicable for the Sub-TLV extension defined in this document.















































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9.  References

9.1.  Normative References

   [IS-IS]    "Intermediate System to Intermediate System Intra-Domain
              Routing Exchange Protocol for use in Conjunction with the
              Protocol for Providing the Connectionless-mode Network
              Service (ISO 8473)", ISO/IEC 10589:2002 Second Edition,
              2002.

   [RFC1195]  Ohta, M., "Use of OSI IS-IS for routing in TCP/IP and dual
              environments", December 1990.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", March 1997.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 2434,
              October 1998.

   [RFC3784]  Smit, H., "Intermediate System to Intermediate System
              (IS-IS) Extensions for Traffic Engineering (TE)",
              June 2004.

   [RFC4020]  Kompella, K. and A. Zinin, "Early IANA Allocation of
              Standards Track Code Points", RFC 4020, February 2005.

   [RFC4971]  Vasseur, J., "Intermediate System to Intermediate System
              (IS-IS) Extensions for Advertising Router Information",
              July 2007.

   [RFC5029]  Vasseur, J. and S. Previdi, "SDP: Session Description
              Protocol", September 2007.

   [RFC5305]  Li, T. and H. Smit, "S-IS Extensions for Traffic
              Engineering", RFC 5305, October 2008.

   [RFC6325]  Perlman, R., Eastlake , D., Dutt, D., Gai, S., and A.
              Ghanwani, "Routing Bridges (RBridges): Base Protocol
              Specification", RFC 6325, July 2011.

   [RFC6326]  Eastlake , D., Banerjee, A., Dutt, D., Perlman, R., and A.
              Ghanwani, "Transparent Interconnection of Lots of Links
              (TRILL) Use of IS-IS", RFC 6326, July 2011.







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9.2.  Informative References

   [TRILL-ML]
              Perlman , R., Eastlake, D., Ghanwani, A., and H. Zhai,
              "RBridges: Multilevel TRILL",
              ID draft-perlman-trill-rbridge-multilevel-03,
              October 2011.












































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Appendix A.  Change Logs

A.1.  draft-wu-trill-lsp-ext-tree-distr-opt-01

   The following are the major changes to previous version
   draft-wu-trill-lsp-ext-tree-distr-opt-00:

   o  Add one new section to discuss Unicast Forwarding.

   o  Add one new section to clarify the motivation to write this draft.

   o  Some other editorial changes.







































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Authors' Addresses

   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: bill.wu@huawei.com


   Weiguo Hao
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: haoweiguo@huawei.com

































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